My perf ceiling in Elm has been in two places:

- Elm CSS and even then, it was on a page with I think hundreds of accordions. We had to use Css.Global to create class based states, then toggle classes.

- Loading a massive library of data and leaving it in the state to make navigation within that library's pages faster. It was a classic tradeoff of upfront vs incremental load time, and we'd just over indexed in one direction.